Pollution, overfishing and climate change are endangering the ocean. We are becoming 'ocean ambassadors' to help spark global marine protection efforts.

The ocean produces half the world’s oxygen, feeds the clouds that give us fresh water, and helps regulate our climate. It brings us food, creates jobs, and even helps make our medicines. Water is life, and 97 percent of it is contained in our seas.

Yet the seas upon which we depend are in trouble. Destructive and illegal fishing practices are resulting in more and bigger boats fishing for fewer and smaller fish. More than 90 percent of the world’s stocks are now fully or over fished. Thirteen million tons of plastic makes its way into the ocean each year — more than 10 percent of all plastic that is made.

Climate change has warmed the ocean to a dangerous degree, causing the loss of half of the world’s coral reefs and even changing the chemistry of the water by making it more acidic. We are feeling the backlash in the hurricanes, typhoons, heatwaves, and floods that are striking us with increasingly regularity. The two of us know from our respective times in office how supposed “once every hundred years” weather events seemed to be happening every year.

We can start with marine protected areas

The good news is that we have some of the answers in front of us. We can draw a line around some of the most precious areas of ocean to create Marine Protected Areas . There can be no industrial fishing or mineral recovery in these MPAs, only local fishing. That can then replenish fish stocks and build resilience to climate change by giving marine flora and fauna places where they can adapt to changing conditions. MPAs are most successful when they are large, isolated, and in place for at least 10 years. And they go hand in hand with our global efforts to combat climate change and ensure sustainable fisheries.

In order to make sure they are successful, we must make sure MPAs and fisheries are properly enforced. GPS and satellite technology, marine patrols, and policing are vital to that. That requires collaboration with other nations. That, in turn, requires them to create their own protected areas, so the responsibility of enforcement can be shared.

At the moment, only 3.7 percent of the world’s ocean has any level of protection, while just 2 percent is strongly protected. We must do better. Indeed, the International Union for Conservation of Nature has recommended safeguarding at least 30 percent of the ocean by 2030 to help maintain biodiversity and sustain the long-term health of marine ecosystems.

That is why we are announcing today that we are co-chairing the Pew Bertarelli Ocean Ambassadors, which aims to support countries’ efforts to secure and implement MPAs.

The two of us believe we can help galvanize global willpower to respond to the crisis in the ocean. We know how important the issue is. We know what it is like to be in office and to be confronted with many competing duties and obligations. But we also know that for any elected leader who has promised to support jobs and grow the economy, there will be no blue economy if we don’t solve the threat to the oceans themselves.

As we’ve said, we need the whole world to get on board. Mankind caused this crisis, and we have to be the ones to end it. It will take the efforts of donor countries and the developing world, governments and businesses, individuals and whole communities, to turn things around. As Ocean Ambassadors, we are determined to play our part.

John F. Kerry, a Visiting Distinguished Statesman at the Carnegie Endowment for International Peace, was U.S. Secretary of State from 2013 to 2017. David Cameron was prime minister of the United Kingdom from 2010-2016. Together they serve as co-chairs for the Pew Bertarelli Ocean Ambassadors group. Follow them on Twitter: @JohnKerry and @David_Cameron